Public threads name their replies and context

Owner decision of 2026-10-06: a persona's public or unlisted post outside any group names its replies
(…/scribbles/{id}/replies) and its conversation's context (FEP-7888), the root's …/context that a reply inherits from
its parent, ours or another server's. Both list only the public and unlisted posts PrivaPub holds; followers-only,
circle, direct and local-only posts name neither and their collections answer 404. Checked live: opening alice's
thread on Mastodon finds carol's reply, which nobody there follows (scenarios/threads.sh).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub.Tests/Http/ThreadCollectionsTests.cs

@@ -0,0 +1,63 @@
+using PrivaPub.Tests.Support;
+using PrivaPub.Tests.Support.Host;
+
+using System.Net;
+using System.Text.Json.Nodes;
+
+namespace PrivaPub.Tests.Http
+{
+	// a public thread names its replies and its conversation (owner decision 2026-10-06), and they list only what is public
+	// or unlisted; a followers-only post names neither
+	[Trait("Category", "Integration")]
+	public sealed class ThreadCollectionsTests : IAsyncLifetime
+	{
+		PrivaPubHost _host;
+
+		public async ValueTask InitializeAsync()
+		{
+			Assert.SkipUnless(MongoFixture.Enabled, MongoFixture.Skip);
+			_host = await PrivaPubHost.Shared();
+		}
+
+		public ValueTask DisposeAsync() => ValueTask.CompletedTask;
+
+		static string PathOf(JsonObject status) => new Uri(status.Text("uri")).AbsolutePath;
+
+		static string[] Items(JsonNode collection) => collection["orderedItems"]!.AsArray().Select(i => i!.GetValue<string>()).ToArray();
+
+		[Fact]
+		public async Task A_public_post_names_its_replies_and_context_which_list_only_public_answers()
+		{
+			var alice = await _host.Mastodon("alice");
+			var carol = await _host.Mastodon("carol");
+			var root = await alice.Status("a public question");
+			var answer = await carol.Status("a public answer", ("in_reply_to_id", root.Text("id")));
+			var hidden = await carol.Status("for my followers", ("in_reply_to_id", root.Text("id")), ("visibility", "private"));
+			var deeper = await alice.Status("and a deeper one", ("in_reply_to_id", answer.Text("id")), ("visibility", "unlisted"));
+
+			var note = (await _host.ActivityPub(PathOf(root))).Ok().Object;
+			Assert.Equal(root.Text("uri") + "/replies", note.Text("replies"));
+			Assert.Equal(root.Text("uri") + "/context", note.Text("context"));
+			var answerNote = (await _host.ActivityPub(PathOf(deeper))).Ok().Object;
+			Assert.Equal(root.Text("uri") + "/context", answerNote.Text("context"));
+
+			var replies = (await _host.ActivityPub(PathOf(root) + "/replies")).Ok().Object;
+			Assert.Equal(new[] { answer.Text("uri") }, Items(replies));
+
+			var context = (await _host.ActivityPub(PathOf(root) + "/context")).Ok().Object;
+			Assert.Equal(new[] { root.Text("uri"), answer.Text("uri"), deeper.Text("uri") }, Items(context));
+			Assert.Equal(alice.Uri, context.Text("attributedTo"));
+			Assert.DoesNotContain(hidden.Text("uri"), Items(context));
+		}
+
+		[Fact]
+		public async Task A_followers_only_post_names_neither_and_serves_neither()
+		{
+			var alice = await _host.Mastodon("alice");
+			var quiet = await alice.Status("for my followers", ("visibility", "private"));
+
+			Assert.Equal(HttpStatusCode.NotFound, (await _host.ActivityPub(PathOf(quiet) + "/replies")).Status);
+			Assert.Equal(HttpStatusCode.NotFound, (await _host.ActivityPub(PathOf(quiet) + "/context")).Status);
+		}
+	}
+}